1. Field of the Invention
The present invention relates to a communication control method, a communication system and a communication controller for using a dummy number to conceal a telephone number.
2. Related Background Art
A system for carrying out a telephone call between a caller terminal and a receiver terminal by concealing either one or both of the telephone number of the caller terminal and the telephone number of the receiver terminal is known (refer to Japanese Patent Application Laid-Open No. 2001-268230, Japanese Patent Application Laid-Open No. 2005-57418, and Japanese Patent Application Laid-Open No. 2008-42588). For example, Japanese Patent Application Laid-Open No. 2001-268230 proposes a system, which has a database for associatively storing at least one of a caller terminal telephone number and a receiver terminal telephone number with a dummy ID, and which makes it possible to select, in accordance with a service code that the caller terminal outputs together with connection destination information, one of three choices: “conceal only the caller number”, “conceal only the receiver number” and “conceal both the caller number and the receiver number”.
In the system described in Japanese Patent Application Laid-Open No. 2001-268230, several numbers must be issued from the public telephone network for each user, because one dummy ID (telephone number for concealment purposes) is needed per user. However, in actuality, since there is a limit to the total number of numbers capable of being issued from the public telephone network, the above system has room for improvement from the standpoint of scalability.
Meanwhile, Japanese Patent Application Laid-Open No. 2005-57418 proposes a system for registering an association between an actual telephone number and a listed number in a relay system, and concealing the actual number from a caller by forwarding an incoming call to the listed number from the caller to the actual telephone number in the relay system. Japanese Patent Application Laid-Open No. 2008-42588 proposes a system for registering an association between an actual telephone number and a listed number in the relay system, and when a call is being forwarded via the relay system, making it possible to display the calling party on the receiver terminal using the listed number after concealing the calling party's actual telephone number by converting the caller telephone number from the actual telephone number to the listed number.
However, there is room for improvement in the technologies of Japanese Patent Application Laid-Open No. 2005-57418 and Japanese Patent Application Laid-Open No. 2008-42588 from the standpoint of security since a call made to a listed number from the receiver side will be received at the telephone number of the calling party associated to this listed number, and in a case where the called party loses his terminal and a third-party makes a call to the listed number left on the call register of the called party's terminal, this call could be connected to the caller terminal associated to this listed number.